Anhydrous calcium base greases containing free fatty acid



United States Patent ANHYDROUS CALCIUM BASE GREASES CON- TAINING FREEFATTY ACID Thomas W. Martinek and Ernest T. Fronczak, Crystal Lake,Ill., assignors to The Pure; Oil Company, Chicago, 11]., a corporationof Ohio No Drawing. Application December 31, 1954 Serial No. 479,244

13 Claims. (Cl. 252-40) This invention relates to anhydrous calcium soapgrease and to the method of preparing the same.

Calcium soap greases made in the conventional man ner from fatty acidsor glycerides such as oleic and stearic acids or glycerides and mixturesthereof, require the presence of Water in order to make the greasehomogeneous. In the absence of water, the soap precipitates from theoil. However, the presence of water in the grease is objectionablebecause such greases have a low dropping point and as a result the useof such greases is limited to operating temperatures below 150 F. Onemethod of overcoming this drawback is to replace-the water by anassociation agent such as calcium acetate. Aonther method is set forthin Patent No. 2,607,734, wherein there is disclosed a method for makinganhydrous calcium grease in which an hydroxy fatty acid is used in thepreparation of the soap stock. Although greases made in accordance withthis patent exhibit satisfactory dropping point and yieldcharacteristics, they have the disadvantage of being rather expensiveand produce a grainy structure unless subjected to a vigorous millingoperation. The grease product of Patent No. 2,607,735 is similar to thatof Patent No. 2,607,734, except that the former additionally contains acalcium salt bf a low molecular weight acid. The grease of Patent No.2,607,735 is subject to the same deficiencies as that of Patent No.2,607,734.

We have now discovered that anhydrous calcium soap greaseslhaving highdropping points and high yields, and which are smooth and of ahomogeneous structure with good stability without milling, can beprepared by using a mixture of high molecular weight hydroxy fatty acidssuch as hydroxy stearic acid, and conventional high molecular weightnon-hydroxy fatty acids having not more than one unsaturated linkage inthe molecule, such as oleic, behenic, erucic, and arachidic acids, inthe preparation of the soap stock. Uniform results in the preparation ofthe grease are assured by controlling the free acidity so that the ratioof soap to free fatty acid in the mixture during grease processing isabout 20 parts by weight of soap to from 0.3 to 1.85% parts of freefatty acid. Not only are such greases of uniform quality but they aresubstantially equal to straight hydroxy stearic acid greases in droppingpoint and other desirable characteristics and yet more economical toprepare because of the lower cost of the fat or fatty acid and the lowercost of processing due to the fact that processing time is considerablyreduced and extensive milling is not neces- Lsary. In some cases theyield is higher. Moreover, the grease exhibits improved compatibilitywith all types of mineral oils over that exhibited by similar grease nothaving requisite free fatty acids present during preparation.

One object of this invention is to prepare a multipurpose, stableanhydrous calcium soap grease.

, ,Another object of this invention is to prepare calcium soap grease ofhigh dropping point and yield.

hydrous calcium soap grease of controlled free acidity and desirabledropping point, yield characteristics and compatibility with mineraloils at a lower cost than heretofore.

Yet another object of this invention is to prepare uniformly desirableanhydrous calcium soap grease of controlled free acidity at a low costby regulating the free acid content during preparation.

A particular point of novelty of this invention is the step ofcontrolling the free fatty acid concentration of said grease during itspreparation in order to completely assure production of a superioranhydrous calcium soap grease. It has been found that when said acidityis not kept within rigidbounds during processing, saidprocessing may bedifiicult and phase separation may occur, so that an unsatisfactoryinferior grease product may result. A critical range of free fatty acidsmust be present at all times after the introduction of the soapconstituents to the base oil in order to assure production of thedesired grease. e

In preparing grease in accordance with our invention, we may employequally advantageously as the base oil any solvent-refined orconventionally-refined hydrocarbon oil or lubricating oil derived frompetroleum oils produced from a Pennsylvania, Mid-Continent, Coastal orother source. The composition of the base oil may vary. The oil may beprepared from a single fraction or admixture of several fractions oflubricating oil and/or extracts thereof. Thus, solvent-refined neutraland bright stocks oils, that is, neutral and bright stock refined withphenol, furfural, nitrobenzeue or similar solvents, may be used, as maythe extracts obtained from such solvent refining processes. The greaseof this invention is thus contrasted with a grease of similarcomposition but not containing the above-described req.1iredconcentration of free fatty acids, in that said latter grease is usuallyobtained in higher yield for a given amount of soap when extract of higharomatic content from the solvent refining of mineral oil bright stockwith phenol, furfural, nitrobenzene or similar solvent is present in thebase oil. The grease of this invention is prepared with equal facilityno matter what base oil or base oils are used. In addition, afterpreparation of the grease of this invention, thinning of said grease maybe accomplished with any one or mixture of two or more of theabove-mentioned types of oils Without fear of in compatibility of saidgrease with the oil or oils. e I

We prefer to prepare a slurry of lime and fatty acids in the base oil.If the base oil has residual acidity due to naphthenic and possiblyother acids present, said residual acidity is first just neutralizedwith aqueous sodium hydroxide at about F. to F. in order that the limewhich is later added will not react with these acids.

After the base oil is neutralized with aqueous sodium hydroxidesolution, sufficient fatty acids are added thereto in order to give afinished grease base having approximately 20 percent byweight of limesoap therein. The fatty acids are added to the heated and neutralizedbase oil at a temperature of about 170-190 F., followed immediately bythe addition of a slurry of hydrated lime in oil. The oil used for theslurry is preferably a neutral oil fraction. The amount of lime shouldbe sufficient to theoretically neutralize all but 0.31.85% by weight oftotal composition of all fatty acids present in the mixture.Alternatively, the fatty acids may be theoretically completelyneutralized and additional fatty acids may be added later on in theprocess. After the addition of the lime slurry, the temperature of themixture rises due to the exothermic reaction between the lime and thefatty the requisite amount of fatty acids to bring the free fatty acidconcentration up to 0.31.85% by weight, calculated on the basis of thegrease containing approximately 20% by Weight of soap. Thus, if thecalcium soaps present in the grease mixture at the time of testingrepresent 40% by weight of the mixture, then 0.6-3.7% byweight freefatty acids should be present. If, conversely, the percent by weight ofsoaps present is then 0.15-0.9% by weight of the free fatty acids arenecessary. Thus, the weight ratio of calcium soap gelation agent in themixture to free fatty acids during preparation of the grease is20:0.3-1.85. After the free fatty acid is properly regulated, thetemperature of the grease mixture is then slowly increased toapproximately 230 to 275 F. and the mixture is cooked at thistemperature until the grease is substantially dehydrated and a smooth,clear plastic grease is obtained. The addition of the fatty acids keepsthe grease from separating into two phases during the dehydrationprocess. The cooking stage will usually requite a considerably shorterperiod of time than six hours. The grease base may then be diluted withfurther quantities of the mineral base oil or oils to desiredconsistency and a finished grease is obtained which does not requiremilling.

Example I As an example of grease prepared in accordance with ourinvention, a grease of the following formulation was prepared:

Raw Materials Wt. Grams Percent Hydrogenated Castor Oil Acids 1.985114.8 Arctic Red Oil 1. 985 114. 8. Hydrated Lime. 0. 553 30. 6 Water 0.081 4. 5 Caustic Soda 0.027 1. 5 Solvent Refined Bright Stock 5 77. 2484272.0 Solvent Refined Neutral (200 Vis.) 18. 119 1002.0

Hydrogenated castor .oil acids comprises mainly hydrogenated riclnoleicacid, the principal constituent of castor oil. Said hydrogenatedrlcinoleic acid is 12-hydroxy'stearic acid. Also, high molecular weightsaturated acids are present in small amount, such as stearic acid.

2 Arctic red oil is mainly oleic acid and may contain minute quantitiesof saturated higher molecular weight; fatty acids.

3 Solvent refined bright stock is bright stock which has been subjectedto solvent extraction with phenol.

4 Solvent refined neutral oil (200 vis.) has been subjected to solventrefining with phenol. 7

*As can be seen from the above formulation, the total content of calciumsoaps was approximately 4%. The grease was prepared by the followingprocedure:

Bright stock in the amount of 300 grams was charged to a grease kettle.Heat was applied and agitation started. When the bright stock reached atemperature of 170 F., a solution of all the caustic soda. in all thewater was added to the kettle. The fatty acids, that is, 109.8 grams ofthe hydrogenated castor oil acids and 109.8 grams of the arctic red oil,were then added While the kettle mixture was held at 190 F. Afteragitation, and while the resulting mixture was still held at 190 F. alime slurry comprising 30.6 grams of the hydrated lime in 100 grams ofthe neutral oil was then added with stirring. This was followed by theaddition of 80 grams of wash neutral oil, that is, oil utilized to washthe container which formerly contained the lime slurry.

Upon addition of the slurry, the temperature of the reaction mixclimbedto about 202 F., due to the exbthermic reaction between the hydratedlime and the fatty acids. Heat was appliedto raise the batch temperatureto 212 F. and said temperature was t e ai a e approximately minutes.Additional heat was then applied to the batch to dehydrate the grease.When the batch temperature reached 214 F., the grease started toseparate into two phases. On determination of the acidity of a sample ofsaid grease at this point it was found to be 1.79% w. as oleic. Anadditional 5 gram amount of each acid was then added, that is, a totalof 3 114.8 grams of hydrogenated castor oil acids and arctic red oil.The acidity was thus adjusted to a weight ratio of calcium soaps to freefatty acids of approximately 20:1.85.

The increased free fatty acids immediately caused the grease to assumeits former homogeneous appearance and dehydration progressed smoothly asthe temperature of the batch was increased. The grease gradually becameclearer and tougher until at 240 F., 1.5 hours after the addition oflime slurry, a translucent, light green, very tough and 'smooth plasticgrease was obtained. This grease was then diluted with the balance ofthe mineral oils to a final soap concentration of 4.0% by weight and afinal free fatty acid concentration of about 0.39% by weight. Total timefor processing was six hours.

The final grease had an ASTM tapered-hole disc penetration of 153unworked, 155 worked and 152 at 2000 strokes.

The grease was found to be particularly suitable as a track-rollergrease for continuous track vehicles and resembled in physicalappearance aluminumsoap greases, but was more stable to working and lesssensitive to changes in temperature than said aluminum-soap greases.

Example II A further non-limiting example of the grease of our inventionis a grease of the following formulation:

Solvent refined 200 viscosity neutral oil 331.17

The grease was prepared according to the process. of our invention asfollows:

The procedure of Example I was followed except that the initial soapconcentration in the base oil mixture was only 20% by weight. Afterpreparation according to Example I, the remainder of the mineral oil wasadded to'reduce the soap concentration to 4% by weight. At this point,the grease contained 0.134 weight percent of free fatty acid, calculatedas oleic acid, and had an ASTM taper-hole disc worked penetration of144. The grease was then further reduced by further addition of brightstock and neutral oil to soap concentrations of the following weightpercentages: 1.12, 1.0, 0.80 and 0.62. At all tested concentrations ofsoap in the base oil, the greases exhibited exceptional stability andwere excellent semifluid saddle lubricants for textile mill use. Nodifiiculties were encountered in the preparation of said greases. Totaltime for the preparation of the greases was 16 hours.

Example III A further non-limiting example of the grease of ourinvention and the process of preparation is a grease of the followingformulation:

Acid-refined gulf coastal mineral oil (viscosity SUS at 210 F.) 5274.0

The procedure of Example Iwas followed, except for the substitution ofthe acid-treated gulf coastal mineral oil for the solvent refined brightstock and solvent refined neutral (200 viscosity) oil mixture. When thefree fatty acid concentration was adjusted so that the grease at 20weight percent concentration contained 0.31.85% by weight, calculated asoleic acid, free fatty acid, no processing difiiculties wereencountered, a high yield of satisfactory grease in a relatively shorttotal process time, under six hours, was obtained, and the grease wascompatible with all types of mineral oils.

The results of a series of comparative tests between greases ofdifferent formulations appear below in Example IV.

Example IV Weight Percent Raw Materials Sample Sample Sample Sample D12-hydroxy stearic acid 1. 88 1. 93 1. 98 2.03. Arctic red oil- 1. 88 1.93 l. 98 2.03. Hydrated llm 0. 51 0. 51 0. 51 0.51. Water 0. 075 0. 0750. 075 0.075. Caustic soda 0. 025 0.025 0. 025 0.025. Intermediateviscosity index 83. 20 83.12 83. 03 82.93.

bright stock. 200 viscosity neutral oil 12. 43 12. 41 12. 40 12.39. Wt.Percent soaps 4. 0 4. 0 4.0 Could not be prepared. Free fatty acids (asoleic acid):

Wt. percent at 32.7% soap 2. 25 2.30 3.03 3.37.

concentration. Wt. percent at 20% soap 1.38 1. 41 1. 85. 2.06.

concentration. Wt. percent at 4.0% soap 0.42 0.43 0.52 Could not beconcentration. prepared. Penetration, unworked 1 106 151 162 Cgulgl gotbe es 0 Penetration, worked, 160 160 101 154 Do.

strokes.

1 Penetration performed by Tapered-Hole Disc method.

The procedure of the preceding examples was followed in the preparationof Samples A, B, C and D, except that the soaps were formed at 32.7%concentration in the base oil, rather than at 20% or 40%. The base oilconsisted of about 64 weight percent bright stock and 36 Weight percentneutral oil. After dehydration of the grease at 230-240 F., it in eachcase was cut back to 4.0 weight percent soap concentration with thebalance of the mineral oils.

It is seen from a study of Example IV that a satisfactory grease can beobtained when the free fatty acid content during preparation of thegrease is kept at a weight ratio to the soap concentration of about1.38-l.85:20. When the free fatty acid-soap ratio went as high as2.06:20 a satisfactory grease could not be prepared, the grease duringprocessing separating into distinct layers and otherwise resistingblending. Satisfactory worked and unworked penetration values wereobtained only for the greases prepared with free fatty acid contents nothigher than 1.85 wt. percent, based on 20 wt. percent concentration ofcalcium soaps. The upper limit of the critical range of free fatty acidsessential to satisfactory grease preparation has therefore beendemonstrated. As previously shown, this range has a lower limit ofapproximately 0.3 wt. percent of free fatty acid per 20 wt. percentconcentration of calcium soaps present.

The grease of our invention can be prepared with uniformity provided thefree fatty acid content is controlled as above-dcscribed, that is, iskept during process ing at a weight ratio to the gelation agent of0.33-1.85 :20. The grease of our invention can be cut back to as low as0.50 weight percent concentration of soap while still retaining itslubricating properties, homogeneity, clarity and smoothness. At thisconcentration the grease is a semi-fluid product.-

The soap of the grease of our invention, although pointed out in theabove examples to be the calcium soaps of a mixture of hydrogenatedcastor oil acids or 12-hydroxy stearic acid and arctic red oil acids, isnot limited to such. The required acids for reaction with the hydratedlime constitute 2575% by weight of acids from the group consisting ofsaturated monoand di-hydroxy fatty acids containing from eighteen totwenty four carbon atoms per molecule, and the remainder or 75-25% byweight consisting of acids from the group consisting of non-hydroxyfatty acids of the non-drying type having not more than one unsaturatedlinkage in the molecule and containing from eighteen to twenty fourcarbon atoms per molecule. As to the saturated acids, it is preferred touse those containing at least twenty carbon atoms per molecule becauseof the greater solubility of the calcium soaps of these acids in mineraloil. All of the soap present in the grease of our invention and utilizedas the gelation agent consists of the calcium soaps of the above-definedtwo types of acids.

We claim and particularly point out as-our invention:

1. An anhydrous calcium soap grease comprising viscous mineral oiltreated with suflicient sodium hydroxide to neutralize naturallyoccurring acids and a gelation agent, substantially all of said gelationagent in the grease, except the soap resulting from the neutralizationof the naturally occurring acids present in the mineral oil, consistingof. calcium soaps of mixed acids from group (1) saturated mono-hydroxyfatty acids containing from eighteen to twenty four carbon atoms per'mole:

cule, and group (2) non-hydroxy fatty acids having not more than oneunsaturated linkage in the molecule and containing from eighteen totwenty four carbon atoms per molecule, the group (1) acids constitutingapproximately 25-75 percent by weight of the mixed acids of said calciumsoaps and the group (2) acids constituting approximately 75-25 percentby weight of the mixed acids of said calcium soaps and the gelationagent being present in an amount which will produce a gelled greasestructure, and free fatty acids selected from the group consisting ofabove-defined group (1) acids and above defined group (2) acids andmixtures thereof in a weight ratio to said gelation agent of0.3-1.85z20.

2. A grease in accordance with claim 1 in which said gelation agent ispresent in the grease in an amount of at least 0.5 percent by weight andin which the free fatty acids amount to at least about 0.02 percent byweight.

3. A grease in accordance with claim 1 in which the group (2) acid hasone double-bonded carbon to carbon linkage.

4. A grease in accordance with claim 1 in which the group (2) acid issaturated acid having at least twenty carbon atoms in the molecule.

5. A grease in accordance with claim 3 in which the group (1) acid is12-hydroxy stearic acid.

6. A grease in accordance with claim 4 in which the group (1) acid is12-hydroxy stearic acid.

7. A grease in accordance with claim 5 in which the group (2) acid isoleic acid.

8. A grease in accordance with claim 7 in which group (1) and group (2)acids of said gelation agent are present in approximately equal amounts.

9. The method of preparing anhydrous calcium soap grease which comprisesthe steps of mixing together a mineral lubricating oil fraction treatedwith suflicient sodium hydroxide to neutralize naturally occurring acidsand at least one hydroxy fatty acid from group (1) acids consisting ofsaturated mono-hydroxy fatty acids having eighteen to twenty four carbonatoms per molecule and at least one non-hydroxy fatty acid from group(2) acids consisting of acids containing not more than one unsaturatedlinkage and having between eighteen and twenty four carbon atoms permolecule, said acids being present in an amount sufficient to gel saidmineral lubricating oil fraction on conversion of said acids to calciumsoaps, and being present in a ratio of 1-3 parts of group (1) acids to3-1 parts by weight of group (2) acids, adding to the mixture withconcomitant heating toabout 210-212" F. until foaming subsides sufi"1-.cient lime to saponify said acids and providing free fatty acids in themixture in a weight ratio to calcium soaps intsaid mixture of 0.3-1.85:20, and cooking the result ing mixture at 230275 F. until the grease issubstantially completely dehydrated.

10. The method of claim 9 in which said lime substantially completelysaponifies all said group (1) and group. (2) acids in the mixture and inwhich said free fatty acids selected from the group consisting of group(:1), and group (2) acids are thereafter added back to thesoap-containing mixture in the desired amount.

11. The method of claim 9 in which said lime saponifies only a portionof said group (1) and group (2) acids present, the remaining portion ofsaid group (1) and group (2) acids in desired amount being present assaid free fatty acids.

v 12;, The method in accordance with claim 9 in which group (1) acid andgroup (2) acid before reaction with said lime are present in the mixturein approximately equal amounts, in which the resulting calcium soaps arepresent during said grease preparation in approximately twenty percentby weight, in which said free fatty acids consist essentially ofapproximately equal amounts of acid from group (1) acids and acid fromgroup (2) acids and the total free fatty acid concentration during saidReferences Citedin the file of this patent UNITED STATES PATENTS2,358,939 Nelson et a1. Sept. 26, 1944 2,413,121 Swensonn Dec. 24, 19462,413,122 Swanson Dec. 24, 1946 2,450,220 Ashburn et a1. Scpt, 2 8, 19482,475,589 Bondi July 12, 1949 2,607,735 Sproule et al. Aug. 19, 19522,613,182 Sproule et al. Oct. 7, 1952 OTHER REFERENCES Manufacture andApplication of Lubricating Greases, Boner, Reinhold Pub. Corp., NY.(1954), pp. 46, 47', 388 and 392.

1. AN ANHYDROUS CALCIUM SOAP GREASE COMPRISING VISCOUS MINERAL OILTREATED WITH SUFFICIENT SODIUM HYDROXIDE TO NEUTRALIZE NATURALLYOCCURRING ACIDS AND A GELATION AGENT, SUBSTANTIALLY ALL OF SAID GELATIONAGENT IN THE GREASE, EXCEPT THE SOAP RESULTING FROM THE NEUTRALIZATIONOF THE NATURALLY OCCURING ACIDS PRESENT IN THE MINERAL OIL, CONSISTINGOF CALCIUM SOAPS OF MIXED ACIDS FROM GROUP (1) SATURATED MONO-HYDROXYFATTY ACIDS CONTAINING FROM EIGHTEEN TO TWENTY FOUR CARBON ATOMS PERMOLECULE, AND GROUP (2) NON-HYDROXY FATTY ACIDS HAVING NOT MORE THAN ONEUNSATURATED LINKAGE IN THE MOLECULE AND CONTAINING FROM EIGHTEEN TOTWENTY FOUR CARBON ATOMS PER MOLECULE, THE GROUP (1) ACIDS CONSTITUTINGAPPROXIMATELY 25-75 PERCENT BY WEIGHT OF THE MIXED ACIDS OF SAID CALCIUMSOAPS AND THE GROUP (2) CONSTITUTING APPROXIMATELY 75-25 PERCENT BYWEIGHT OF THE MIXED ACIDS OF SAID CALCIUM SOAPS AND THE GELATION AGENTBEING PRESENT IN AN AMOUNT WHICH WILL PRODUCE A GELLED GREASEDSTRUCTURE, AND FREE FATTY ACIDS SELECTED FROM THE GROUP CONSISTING OFABOVE-DEFINED GROUP (1) ACIDS AND ABOVEDEFINED GROUP (2) ACIDS ANDMIXTURES THEREOF IN A WEIGHT RATIO TO SAID GELATION AGENT OF0.3-1.85:20.